In recent years, there have been rapidly developed a vehicle remote control apparatus capable of opening and closing a vehicle door lock without inserting a key into the door. FIG. 6 is a configuration diagram of a conventional vehicle remote control system and FIG. 7 is an operation sequence diagram of the vehicle remote control apparatus shown in FIG. 6. In other words, FIG. 7 shows a sequence of outputting of signals from various units. FIG. 8 and FIG. 10 are also configuration diagrams of the conventional vehicle remote control system in different situations and FIG. 9 and FIG. 11 are operation sequence diagrams in the respective situations.
Near the driver's door and near the assistant driver's door of the vehicle, there are respectively provided antennas 11, 12 for transmitting signals for authentication. Further, within or near a rear bumper on the driver's side and within or near the bumper on the assistant driver's side, there are provided antennas 13, 14. Antennas 11, 13 have communication ranges 11A, 13A, respectively.
In the configuration described above, suppose now that owner 5 of the vehicle carrying a mobile device 4 including a radio terminal assigned with an identification code special to the vehicle approaches the vehicle from the driver's side as shown in FIG. 6. When owner 5 touches the door on the driver's side, outside door switch 2 is turned on and this ON-signal is transmitted to controller 1. Thereupon, controller 1 outputs authentication request signal 701.
Since mobile device 4 is present within range. 11A at this time, mobile device 4 outputs authentication response signal 702. Authentication signal receiver (hereinafter called “receiver”) 8 receives response signal 702, and when this signal is verified against the registered code and validated, receiver 8 outputs door lock opening signal 703 to controller 1, whereby the door lock is released.
Then, suppose that controller 1 outputs authentication request signal 901 from antenna 11 when mobile device 4 is positioned at the rear of the vehicle as shown in FIG. 8. Since mobile device 4 is present out of range 11A at this time, mobile device 4 does not output an authentication response signal. In such a case, controller 1 outputs authentication request signal 902 from antenna 13 after a predetermined period of time. Since mobile device 4 is now present within range 13A where authentication request signal 902 is communicatable, it outputs authentication response signal 903, and receiver 8 receives response signal 903. Receiver 8 verifies and validates the received signal and outputs door lock opening signal 904 to controller 1, whereby the door lock is released.
Likewise, when owner 5 carrying mobile device 4 approaches the vehicle from the assistant driver's side, an ON-signal of outside door switch 3 on the assistant driver's side is transmitted to controller 1. Controller 1 outputs an authentication request signal from antenna 12. If mobile device 4 is present within the communication range of antenna 12, mobile device 4 outputs an authentication response signal. Receiver 8 receives this response signal and if the signal matches with the registered code, it outputs a door lock opening signal to controller 1 and thereby the door lock is released.
Further, when owner 5 carrying mobile device 4 approaches the vehicle from the rear of the vehicle, an ON-signal of outside door switch 7 at the rear of the vehicle is transmitted to controller 1, and controller 1 outputs an authentication request signal from antenna 13, 14. If mobile device 4 is present within the communication range of antenna 13 or antenna 14, mobile device 4 outputs an authentication response signal. Receiver 8 receives this signal and outputs a door lock opening signal to controller 1, if it matches with the registered code, thereby, the door lock is released. Such a vehicle remote control apparatus as described above is disclosed, for example, in Japanese Patent Unexamined Publication No. 2003-106019.
However, there is a problem with the above described conventional system as follows. In FIG. 10, owner 5 carrying mobile device 4 is within the communication range 13A of antenna 13 at the rear of the vehicle on the driver's side but the owner is just present there with no intention to open a door of the vehicle. For some time in the beginning, there is no response made to authentication request signal 1101 output from antenna 11 and, hence, door lock opening signal 1104 is not output. However, if stranger 6 approaches the vehicle from the driver's side and turns on switch 2 unnoticed by owner 5, mobile device 4 transmits authentication response signal 1103 when authentication request signal 1102 is output. Namely, authentication is validated because mobile device 4 is present within communication range 13A of antenna 13. Thus, the door lock is released and the door is opened by stranger 6 while it is unnoticed by owner 5.